[A380X] Better AP Disconnect Logic

[pilotseyea350]

Aircraft Version

Development

Build info

{
    "built": "2024-09-30T16:42:48+00:00",
    "ref": "refs/heads/a380x-experimental",
    "sha": "c090953517e912d5833db4783ac671c61fb1db69",
    "actor": "aguther",
    "event_name": "manual",
    "pretty_release_name": "a380x-experimental:c0909535",
    "version": "a380x-v0.12.0-a380x-experimental.c090953"
}

Describe the bug

Currently when disconnecting the autopilot, the events are as follow:

• Autopilot Disconnect
• 3 Autopilot disconnect chimes
• 3 Landing Capability Downgraded clicks

No matter the number of click on the sidestick takeover button, the sequence is the same

Expected behavior

When disconnecting the autopilot, the sequence should be:

• Autopilot Disconnect
• Master Warning Light should come on and stay on until the sidestick takeover has been clicked a second time or the master warning button has been pushed
• Autopilot disconnect chimes until the sidestick takeover has been clicked a second time or the master warning button has been pushed
• 3 Landing Capability Downgraded clicks if switching from an ILS CAT3 approach to an ILS CAT1 (iirc)

Steps to reproduce

1. Fly above 400ft AGL
2. Engage autopilot
3. Disengage autopilot
4. Observe the events after autopilot is off

References (optional)

https://www.youtube.com/watch?v=qcXQKQukxkI&t=59s

& many other A380 cockpit landing videos

Additional info (optional)

No response

Discord Username (optional)

PilotEyesA350

[flogross89]

The exact logic is a little bit more complicated, and should be implemented in the FWS (together with the AP OFF memo, ...)

[pilotseyea350]

Yeah I assumed it was a bit more in complex than that. Just opened it to highlight it ! Do we have a FWS PR or issue opened for this already ?

[flogross89]

All good, no there's no issue for it. Just commenting for future implementation

[lukecologne]

This issue is not exclusive to the A380X btw, the A32NX suffers from the same simplistic logic

[henrybungee]

Found this in the A319/20/21 FCOM. I can't imagine that the autopilot disconnect logic is any different in the A380.

The only time the triple click should be audible after disconnecting the autopilot should be when the autoland FMA mode is reverted to CAT I.

I don't remember if the triple click logic is implemented into the FMA in general (any FMA mode reversion, e.g. turning the flight directors off, heading select while using a managed climb or descent mode) but if not that's also something that could help improve the AP disconnect logic.

[flogross89]

In the meantime, the FWS logic for AP disconnect has been overhauled for the A380X, it should be fairly accurate now. It is a little different than the a320, for example there’s no minimum CRC time, it can be cancelled right away.

One exception though: The triple click logic is still inaccurate, because we would need changes on the AP/FG side for that.
So future fixes should concentrate on the triple click.